Method for Hydrodynamic Stimulation of the Bottom of a Seam

ABSTRACT

The method can be used in the oil-producing industry for intensifying the production of oil and for increasing the intake capacity during the working of the bottom region of a seam and completion of wells. For producing pressure draw-down and repressuring cycles at the well bottom there is periodically changed the direction of flow of working liquid using controlled movement of jet pump. The value of maximal pressure draw-down is regulated, and periods of pressure draw-down and repressuring action are implemented with equal values of volumes of the inflow and the liquid pumpable into the seam in one cycle. These volumes in each subsequent cycle are increased. The cycles are continued until the increase in the values of the liquid volumes ceases. Chemical reagents are then pumped into the seam. If necessary, the cycles are repeated. The stimulation of the bottom region of the seam is completed with a pressure draw-down. 
     14 variants of formula.

PERTINENT ART

The invention applies to the oil-producing industry and can be used for intensifying the production of oil and for increasing the intake capacity during the working of the bottom region of a seam and completion of wells with complex methods of treatment using special hydrodynamic equipment.

PREVIOUS LEVEL OF TECHNOLOGY

There is known the method of dynamic processing of the bottom regions (RU No. 2322578, Apr. 20, 2008), including lowering on flow column of equipment set, consisting of accumulator of pulse pressure, packer, circulating valve and jet pump. Beforehand the packer is set in operating position, then by raising a little of the pipe string the circulating valve is opened and operational reagents are pumped into the pipe string. Then the pipe string is lowered and the circulating valve is closed, and reagents are extruded by liquid from pump unit into the bottom region at hydroimpulsive impact. Immediately after extruding reagents there is switched the supply of liquid from pump unit into hole annulus and the liquid from the bottom region to the well head is pumped out by jet pump. Then again the pipe string is raised a little, the circulating valve is opened and the second cycle of treatment is executed with increase in volume of pumped in reagent. This method allows to increase the efficiency of conducting acid bottom-hole treatment due to cyclic, hydroimpulsive pumping and recovery of reagents in pressure draw-down mode with subsequent cyclic increase of radius of impact, not waiting for sludging of reaction products, during one round-trip operation. Among deficiencies of the method one can mention the need for additional manipulation with pipe string after packer seating for pumping in and extruding of reagents using circulating valve, the need for pumping in of liquid under pressure into hole annulus for operation of jet pump, which limits application of this method by types of wells and depth of pay zones, as well as irregular value of maximal pressure draw-down, which could lead to narrowing of pores, closing of cracks and violation of integrity of casing.

There is known the method of hydrodynamic stimulation of well bore zone (RU No.2221170, Jan. 10, 2004), when to the well on flow column there are lowered a liner, a packer and a jet pump, these packer and jet pump are placed above the roof of pay zone and the packer is released, by pump unit there is periodically abruptly supplied working substance into the nozzle of jet pump and pressure draw-down is applied to the pay zone, action of this pressure draw-down onto the seam is kept by constant supply of working substance into the nozzle of jet pump at set pressure of pump unit, then by abrupt termination of supply of working substance into the nozzle of jet pump there is very rapidly reestablished the hydrostatic pressure of liquid column, accompanied by water hammer to the pay zone, at that the pressure of liquid column is set higher than formation pressure. This described above cycle of stimulation of well bore zone by pressure draw-down and pressure of hydrostatic liquid column is repeated, the number of cycles “pressure draw-down +hydrostatic pressure recovery” is defined by degree of restoration of permeability of well bore zone by periodic check measurements of well production before and in the process of cyclic stimulation of well bore zone, at that, if during two last check measurements the well production did not increase, then the work is terminated. Cyclic change of pressure onto well bore zone allows for alternating stimulation of the seam with forming water hammer, which leads to increase of radius and quality of treatment of well bore area. Stimulation is accompanied by periodic measurements of production for control of efficiency of conducted treatment. Among deficiencies of this method one could mention force impact of pressure on casing above packer, which limits the range of alternating treatment of the seam. Pressure draw-down action is possible only at constant supply of working substance into the nozzle of jet pump, and energy of impulse of water hammer is not concentrated in the interval of pay zone, but is spread along all under packer space.

There is known the method of hydrodynamic stimulation of the seam (RU No.2360103, Jun. 27, 2009), when on flow column above the perforation interval zone there are placed a jet pump and a packer, the packer is released and working fluid is pulsating fed into the nozzle of jet pump for producing pressure draw-down in pay zone. Then repressuring is applied to the pay zone by supplying working liquid into annular space through jet pump into under packer space and seam in the amount higher than the amount of formation pressure. This stated above cycle is repeated for stimulation of well bore zone with pressure draw-down and repressuring. Flow and pressure in under packer zone are measured and there is defined the degree of restoration of permeability of well bore zone by increase in well production, at that stimulation of the seam is terminated, when well production becomes constant. This method allows to use cyclic change of pressure in the interval of pay zone, which increases the intensity of hydrodynamic stimulation, especially in the mode of periodic pulsations. Among deficiencies of this method there would be limitations in the value of created repressuring, exceeding the value of formation pressure, because fluid head at repressuring is produced in casing column having low value of pressure testing. That is why the need to achieve values of repressuring higher than formation pressure leads to narrowing of this method application in types and depth of wells. According to this method before the jet pump there is placed a pulsator, where is lost a major part of head of pumped in working liquid, that is why the amount of increase in production is limited due to dependence of production on the head at the nozzle of jet pump.

As the most similar to our invention in its technical essence and achieved results there could be mentioned the method of hydrodynamic stimulation of well bore zone (RU No.2222716, Jan. 27, 2004), when to the well there are lowered a packer and a jet pump placed on flow column, these jet pump and packer are placed above the roof of pay zone and the latter has the packer released. By pump unit at set pressure there is periodically abruptly supplied working liquid into the nozzle of jet pump, pressure draw-down is produced and kept at pay zone by constant supply of working fluid, by abrupt switching of working liquid supply from pipe string into under packer space there is produced repressuring at pay zone as pressure pulse from water hammer. At that the value of pressure in impulse is set higher than the value of formation pressure. Cycles of stimulation with pressure draw-down and repressuring are repeated with periodic check measurements of well production. The work is terminated, if during last two measurements well production didn't change. This method is designed for increasing reliability and capacity at stimulation for restoration of permeability of well bore zone for the purposes of increasing production of producing and intake capacity of intake wells. Among advantages of the method there could be mentioned regulation by flows in the process of work, which increases efficiency of alternating hydrodynamic impact in conjunction with water hammers at well bore zone, whose permeability is periodically controlled by value of production in the mode of pressure draw-down. The need for application of additional drive, for example a borehole cable, for regulating flows of working liquid and forming periodic pressure draw-down and repressuring worsens reliability in control of switching and limits application of this method by type, for instance in horizontal, and by depth wells. Disadvantage of this method is low value of repressuring due to hydraulic connection with annular space above packer, which limits application of this method by range of created alternating impact and pressure value at pumping in to the seam of chemical reagents. Forming of pressure pulses is possible only in a short interval of time at switching of flow direction, energy of the pulse is not concentrated in the interval of pay zone, but is spread all over under packer space, worsening efficiency of impact.

ESSENCE OF INVENTION

The objective of this invention is to ensure effectiveness increase and functional reliability of method of stimulation, enhancement of technology options and conditions for application in various types of wells at increase of intensity of hydrodynamic stimulation.

Technical result is achieved as in the known method of hydrodynamic stimulation of the bottom region of the seam, including lowering to the well of body with jet pump, isolation of hole annulus from internal space of flow column above the roof of pay zone, periodical change of direction of the flow of working liquid in the well for producing pressure draw-down and repressuring cycles, defining volumes of pumped out liquid at pressure draw-down and introducing fluid pulse to pay zone at repressuring, according to invention the direction of flow of working liquid in the well is changed at controlled movement of jet pump in the body, maximum pressure draw-down value is adjusted, by amount of volume of pumped into the seam liquid there is defined the period of repressuring action, and periods of pressure draw-down and repressuring action are implemented with equal values of volumes of the inflow and the liquid pumpable into the seam in one cycle, at that stated volumes in each subsequent cycle are increased, the cycles are continued until the increase in the values of the liquid volumes ceases, chemical reagents are then pumped into the seam, if needed these cycles are repeated and the stimulation of the bottom region of the seam is completed with a pressure draw-down.

In order to increase the intensity of stimulation of the bottom region of the seam for the purposes of softening of colmatant and balancing of filtration profile it is appropriate to produce in cycles of pressure draw-down and repressuring of additional hydraulic pulses with energy concentration on the wall of casing column in the interval of pay zone.

Movement of jet pump for changing direction of the flow in the well can be controlled both remotely and automatically, which considerably widens application options of this method in vertical and horizontal wells. Remote control of movement is achieved through wireline technique. Automatic control is achieved by supply of working liquid into the nozzle of jet pump and elastic force of spring returning jet pump to initial position when supply is stopped.

For effective application of this method at producing pressure draw-down and repressuring cycles in wells of different design and its application in combination with other technologies for working of the bottom region of the seam the working liquid can be supplied to the well either through hole annulus or along the flow column.

At introduction of hydrodynamic stimulation in wells with multihorizon development it would be appropriate to apply selective by interval treatment using additional isolation of hole annulus below lower boundary of pay zone.

It would be appropriate simultaneously with pulse action at repressuring to exceed the value of rock pressure at the depth of chosen interval of pay zone for producing additional system of microcracks in the bottom region of the seam and increase of filtration area, as well as for regeneration of earlier existed cracks. At that in order to exceed rock pressure more effectively there can be used breakdown agents, for example acid-oil emulsions, and for registration of current hydrodynamic parameters in the interval of treatment it would be appropriate to place there a recording instrument.

Chemical reagents can be pumped into the flow column in pressure draw-down mode at operation of jet pump and circulation of liquid with pouring out of the well in the wellhead, and to pump in chemical reagents into the seam—in the mode of repressuring at closed hole annulus in the wellhead. It would be appropriate at the end of treatment to clean the bottom region from reaction products (of chemical reagents) with their removal to the wellhead in the mode of regulated pressure draw-down. In order to increase the impact of chemical reagents they should be pumped into the seam as a part of gas-liquid mixtures.

Finishing of hydrodynamic stimulation of the bottom region of the seam in the mode of regulated pressure draw-down is possible by lowering level of liquid in the well, for example using compressor.

For evaluation of efficiency of works for increasing well production before and after treatment it would be appropriate to record bottom hole pressure buildup using placed there beforehand a down hole instrument.

Essence of offered method for hydrodynamic stimulation of the bottom region of the seam is in changing direction of working liquid flow in the well using controlled movement of jet pump, at that the whole flow changes its direction, and not just a part of it, as in the prototype, which increases efficiency of application of hydraulic power of the flow for producing pressure draw-down or forming fluid pulse in seam's interval. Application of controlled remotely or automatic movement of jet pump allows to set the frequency of changes in direction of flow for producing pressure draw-down and repressuring cycles with alternating pressure stimulation of porous rock structure. Such modes allow to conduct controlled along the radius penetration of impact into porous space of the bottom region. Cyclic impact with alternating pressure at the well bottom at equal values of volumes of the inflow and the liquid pumpable into the seam provides for phased and effective cleaning of porous space of the bottom region with substitution of volume of contaminated formation liquid by the same volume of clean pumped in liquid. Subsequent pumping in of chemical reagents at alternating impact on the seam increases the efficiency of their penetration and considerably shortens duration of works. Maximal value of pressure draw-down is regulated not only with the use of head produced by pump unit, but also with the use of additional device, beforehand adjusted for actuation at achievement of minimally permissible value of pressure at well bottom, preventing considerable narrowing of pores and closing of cracks, as well as violation of integrity of casing at considerable collapsibility loads. Such device can be a pressure regulator with operation principle based on keeping calculated pressure drop.

THE BEST VARIANT FOR REALIZATION OF THIS INVENTION

In advance there is chosen the method for supply of liquid into the well, for example through flow column and, for example automatic variant of movement of jet pump for flow control in the well. At the wellhead there is assembled a corresponding equipment set and is lowered into the well on flow column subsequently fixed one by one the body, in which there is installed a jet pump with a switch of flow direction, a pressure regulator, a packer with anchor and a liner with flow regulator. The packer with anchor is placed above the roof of pay zone and is set into operative state so that the liner was in perforation interval. Discharge line from pump and oxygen units is connected with flow column, and intake line is connected with graduated tank filled in with working liquid. Output line from well's hole annulus is connected with graduated tank. Then by pump unit there is supplied working liquid under pressure to the flow column to the nozzle of jet pump and is produced regulated in amount pressure draw-down in the interval of the seam, accompanied by retrieval of inflow of formation liquid and its delivery together with working liquid circulating along hole annulus to the wellhead into the graduated tank. There is defined the value of inflow from the seam. Then the flow of working liquid is stopped, at that under action of spring's elastic force the jet pump is moved, which at further supply of working liquid switches the flow direction past nozzle of jet pump under packer into liner and then to the seam. In repressuring mode to the bottom region there is pumped in the volume of working liquid equal to retrieved volume at pressure draw-down. Again supply of working liquid is stopped, automatically due to spring's force the jet pump is moved. At subsequent supply of liquid the direction of flow is switched into the nozzle of jet pump and retrieval of inflow of formation liquid in volume larger than initial one. Periodic switching on and off of working liquid supply into the well is accompanied with forming of hydraulic pulses, directed through liner to the treated interval, and continues till the moment, when amount of inflow production from the seam and correspondingly amount of its intake capacity stop increasing. Then at liquid supply into the nozzle chemical reagents are pumped into the flow column, and at switching of flow past jet pump under packer these reagents are squeezed into the seam. Final cleaning of porous space from reaction products is done in the mode of regulated pressure draw-down with liquid inflow from the seam to the wellhead.

At achievement of required intake capacity or production of the well the treatment is stopped. The packer is unset and equipment set is hoisted to the surface. So, treatment is conducted during one round-trip operation with one surface connection.

Application of this method in the oil-producing industry.

Effectiveness of proposed method was confirmed by development work at the well No.1184 of Vatinsk field. The well exposed the oil-bearing formation YuV1 (IOB1) with temperature at well bottom 95° C., presented in perforation interval 2,515-2,529 m by mudded-off sandy and aleurolitic interlayers with average permeability of 0.0044 square micrometers. Before bottom-hole treatment the well was exploited producing liquid 6.0 m³/day and water intrusion 4%; productivity factor was 0.044 m³/day.atmospheric. Formation pressure was 18.4 MPa.

For bottom-hole treatment into the well there was lowered a flow column with a set of equipment on it consisting of:

Body (in which there were installed a jet pump with nozzle, mixing chamber and diffuser and flow switch);

Pressure regulator;

Packer with anchor;

Liner with flow regulator and additional generator of pressure pulses with concentrator.

to As working liquid there was used stock tank oil with density 0.86×10³ kg/m³. Pressure regulator was adjusted for keeping pressure in the interval of impact not lower than 4.0 MPa. Packer with anchor was placed at the depth 2,450 m, and liner at the depth 2,521 m.

The first cycle: with the use of working liquid from graduated tank by pump unit there was caused in the well the flow circulation through flow column, nozzle of jet pump, hole annulus, graduated tank. At pressure draw-down of the seam there was caused inflow from the seam with production 6.0 m³/day and 0.5 m³ of liquid was pumped out. Then supply of working liquid was stopped, at that jet pump automatically switched direction of flow under packer into liner and further to the seam. In the mode of repressuring into the seam was pumped in 0.5 m³ of clean liquid.

The second cycle: at pressure draw-down mode there was caused inflow from the seam with production 7.2 m³/day and 1.0 m³ of liquid was pumped out. In the mode of repressuring into the seam was pumped in 1.0 m³ of clean liquid.

The third cycle: at pressure draw-down mode there was caused inflow from the seam with production 9.6 m³/day and 1.5 m³ of liquid was pumped out. In the mode of repressuring into the seam was pumped in 1.5 m³ of clean liquid.

The fourth cycle: at pressure draw-down mode there was caused inflow from the seam with production 9.6 m³/day and 1.5 m³ of liquid was pumped out. In the mode of repressuring into the seam was pumped in 1.5 m³ of clean liquid.

In pressure draw-down mode there was pumped in into flow column 4 m³ of hydrochloric acid +3.6 m³ of mud acid, jet pump was transferred to position of repressuring, we continued with pumping in of 2.4 m³ mud acid and 8 m³ of working liquid were squeezed into seam. After reaction of acid during 2 hours there was applied draw-down action for cleaning from reaction products. Inflow production amounted to 14-15 m³/day.

After bottom-hole treatment the well was returned to exploitation with stable production of 16 m³/day and water intrusion 11%; productivity factor was 0.14 m³/day.atmospheric. 

What is claimed:
 1. Method of hydrodynamic stimulation of a bottom region of a seam comprising the steps of lowering to the well of body with jet pump, isolation of hole annulus from internal volume of flow column above the roof of pay zone, periodical change of direction of the flow of working liquid in the well for producing pressure draw-down and repressuring cycles, defining volumes of pumped out liquid at pressure draw-down and introducing fluid pulse to pay zone at repressuring, in this method direction of flow of working liquid in the well is changed at controlled movement of jet pump in the body, maximum pressure draw-down value is adjusted, by amount of volume of pumped into the seam liquid there is defined the period of repressuring action, and periods of pressure draw-down and repressuring action are implemented with equal values of volumes of the inflow and the liquid pumpable into the seam in one cycle, at that stated volumes in each subsequent cycle are increased, the cycles are continued until the increase in the values of the liquid volumes ceases, chemical reagents are then pumped into the seam, if needed these cycles are repeated and the stimulation of the bottom region of the seam is completed with a pressure draw-down.
 2. Method according to claim 1, wherein in pressure draw-down and repressuring cycles there are produced additional hydraulic pulses, whose energy is concentrated on the wall of casing column in the interval of pay zone.
 3. Method according to claim 1, wherein for changing direction of working fluid flow in the well jet pump in the body is moved remotely using wireline technique.
 4. Method according to claim 1, wherein for changing direction of working fluid flow in the well the jet pump in the body is moved automatically—using supply of working fluid into nozzle of jet pump in one direction and elastic force of spring returning jet pump in opposite direction at termination of supply.
 5. Method according to claim 1, wherein for producing pressure draw-down and repressuring cycles working liquid is supplied to the well through hole annulus.
 6. Method according to claim 1, wherein for producing pressure draw-down and repressuring cycles working liquid is supplied to the well through flow column.
 7. Method according to claim 1, wherein hole annulus is additionally isolated below lower boundary of pay zone.
 8. Method according to claim 1, wherein value of repressuring is set higher than value of rock pressure at the depth of chosen interval of pay zone.
 9. Method according to claim 6, wherein for exceeding value of rock pressure into pay zone there are pumped in breakdown agents.
 10. Method according to claim 1, wherein the process of treatment in chosen interval of pay zone the hydrodynamic parameters are registered.
 11. Method according to claim 1, wherein chemical reagents are in advance pumped in into flow column at pressure draw-down, and to the seam they are pumped in at repressuring.
 12. Method according to claim 1, wherein chemical reagents are pumped into the seam as a part of gas-liquid mixtures.
 13. Method according to claim 1, wherein stimulation of the bottom region of the seam is finished in the mode of regulated pressure draw-down with pumping out of formation fluids.
 14. Method according to claim 1, wherein stimulation of the bottom region of the seam is finished in the mode of regulated pressure draw-down by lowering level of liquid in the well.
 15. Method according to claim 1, wherein before and after hydrodynamic stimulation there is registered bottom hole pressure buildup in the interval of pay zone. 